IP Numbers, caching?

P

pehu

Perch
Hi!

I have had some problems with the change of ns IP. Since yesterday I can see my domains are working well.

But, still I have some people saying they can?t access their sites. I have told them to delete their cache memorys and empty their temporary internet file folders in their browsers thinking that it is a caching problem. But some says the problem is still there.

Can it possibly be so that their own ISP?s have caching? I don?t know how this works, but can someone give me some info about it. Would be good to hav something to inform my clients about it.

Thanks! Petri
 
Their ISP's nameservers almost certainly also do caching. However, I'm not sure what they would be caching, since these domains failed to resolve at all up until recently..

However, you can (usually) find out exactly what's going on. Find out their ISP's nameserver first, then you can use nslookup (start - run... - nslookup) to find out if the cached IP is incorrect, why and how long the incorrect information will be cached:

Code: 
[b]> server ns1.theirisp.com.[/b]
Default Server:  ns1.theirisp.com
Address:  xxx.xxx.xxx.xxx

[b]> set debug[/b]
[b]> www.customerdomain.com.[/b]
Server:  ns1.theirisp.com
Address:  xxx.xxx.xxx.xxx

------------
Got answer:
    HEADER:
        opcode = QUERY, id = 2, rcode = NOERROR
        header flags:  response, want recursion, recursion avail.
        questions = 1,  answers = 1,  authority records = 2,  additional = 2

    QUESTIONS:
        www.customerdomain.com, type = A, class = IN
    ANSWERS:
    ->  www.customerdomain.com
        [color=red]internet address = xxx.xxx.xxx.xxx
        ttl = 86262 (23 hours 57 mins 42 secs)[/color]
    AUTHORITY RECORDS:
    ->  customerdomain.com
        [color=orange]nameserver = ns1.yourdomain.com
        ttl = 80392 (22 hours 19 mins 52 secs)[/color]
    ->  customerdomain.com
        [color=orange]nameserver = ns2.yourdomain.com
        ttl = 80392 (22 hours 19 mins 52 secs)[/color]
    ADDITIONAL RECORDS:
    ->  ns1.yourdomain.com
        [color=orange]internet address = xxx.xxx.xxx.xxx
        ttl = 82388 (22 hours 53 mins 8 secs)[/color]
    ->  ns2.yourdomain.com
        [color=orange]internet address = xxx.xxx.xxx.xxx
        ttl = 82388 (22 hours 53 mins 8 secs)[/color]

------------
Non-authoritative answer:
Name:    www.customerdomain.com
[color=blue]Address:  xxx.xxx.xxx.xxx[/color]

What you type is in bold (notice the dots after the hostnames).
The exact debug output will most likely differ, but what you're looking for is the TTL line marked in red, just under the resolved IP answer. If the IP is wrong, it may take up to that time for it to resolve correctly for that particular ISP.

The parts marked in orange may not be present, but they show the nameservers that were originally used to retrieve this information at the time it was cached. It's possible that cached IPs for the nameservers are still being used, in which case the TTLs under ADDITIONAL RECORDS will give you the maximum amount of time it will take for this to correct itself.

However, considering ISP nameservers are usually fairly heavily used by a wide variety of customers, it's very possible that any incorrect information will be pushed out of the cache long before that.
 
Great, Thanks!

I try this and I get an answer but I can?t really find out what it says.
Can you possibly see what it tells?

This is the output I get:

> server ns1.bredband.com.
Default Server: ns1.bredband.com
Address: 195.54.122.193

> set debug
> www.biraxel.se.
Server: ns1.bredband.com
Address: 195.54.122.193

------------
Got answer:
HEADER:
opcode = QUERY, id = 3, rcode = NOERROR
header flags: response, want recursion
questions = 1, answers = 0, authority records = 7, additional = 10

QUESTIONS:
www.biraxel.se, type = A, class = IN
AUTHORITY RECORDS:
-> se
nameserver = A.NS.se
ttl = 113782 (1 day 7 hours 36 mins 22 secs)
-> se
nameserver = B.NS.se
ttl = 113782 (1 day 7 hours 36 mins 22 secs)
-> se
nameserver = C.NS.se
ttl = 113782 (1 day 7 hours 36 mins 22 secs)
-> se
nameserver = F.NS.se
ttl = 113782 (1 day 7 hours 36 mins 22 secs)
-> se
nameserver = G.NS.se
ttl = 113782 (1 day 7 hours 36 mins 22 secs)
-> se
nameserver = D.NS.se
ttl = 113782 (1 day 7 hours 36 mins 22 secs)
-> se
nameserver = E.NS.se
ttl = 113782 (1 day 7 hours 36 mins 22 secs)
ADDITIONAL RECORDS:
-> A.NS.se
AAAA IPv6 address = 2001:698:9:301::53
ttl = 113782 (1 day 7 hours 36 mins 22 secs)
-> A.NS.se
internet address = 192.36.144.107
ttl = 113782 (1 day 7 hours 36 mins 22 secs)
-> B.NS.se
internet address = 192.36.133.107
ttl = 113782 (1 day 7 hours 36 mins 22 secs)
-> C.NS.se
internet address = 192.36.135.107
ttl = 113782 (1 day 7 hours 36 mins 22 secs)
-> F.NS.se
AAAA IPv6 address = 2001:6b0:7::53
ttl = 113782 (1 day 7 hours 36 mins 22 secs)
-> F.NS.se
internet address = 192.36.125.53
ttl = 113782 (1 day 7 hours 36 mins 22 secs)
-> G.NS.se
AAAA IPv6 address = 2001:6b0:8:1::53
ttl = 113782 (1 day 7 hours 36 mins 22 secs)
-> G.NS.se
internet address = 130.242.94.18
ttl = 113782 (1 day 7 hours 36 mins 22 secs)
-> D.NS.se
internet address = 81.228.11.57
ttl = 113782 (1 day 7 hours 36 mins 22 secs)
-> E.NS.se
internet address = 81.228.10.57
ttl = 113782 (1 day 7 hours 36 mins 22 secs)

------------
Name: www.biraxel.se
Served by:
- A.NS.se
192.36.144.107
se
- B.NS.se
192.36.133.107
se
- C.NS.se
192.36.135.107
se
- F.NS.se
192.36.125.53
se
- G.NS.se
130.242.94.18
se
- D.NS.se
81.228.11.57
se
- E.NS.se
81.228.10.57
se
 
You can email me with the domains that you think are having issues and I'll check out its DNS and see if there are any issues.

However its highly unlikely if you are able to access and ping the sites at the moment
 
It looks like that particular ISP has protected their nameservers from outside usage, and are referring you to the servers for the Swedish top level domain.

You can't get the information as I showed you without actually having a connection through that ISP then :(

For what it's worth: settings from your side look ok to me and the page is loading fine from here.
 
Thanks a lot for help. I have talked with my client and she is just reporting that her sites runs fine now. :)
 
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